Question

In 5.1g of a substance is added to 36g of water The vapour pressure of water decrease from 442mmofHg to 410mmofHg Find the molar mass of substance​

Answer 1

Answer:

Molar mass of substance = 32.67g

Explanation:

Vapour pressure of Pure water ($P_{\°}$) = 442 torr

Vapour of solution ($P_{s}$) = 410

Weight of solute = 5.1g & weight of water = 36g

=> $\frac{P_{\°}-P_{s}}{P_{s}} = \frac{n}{N}$ (where n = moles of solute & N = moles of solvent)

Let us consider the molar mass of solute as 'x'

=> $\frac{442-410}{410}=(\frac{5.1}{x} )(\frac{18}{36} )$

=>$\frac{32}{410}=\frac{5.1}{2x}$

=> $x=\frac{(5.1)(410)}{(2)(32)} = 32.67g$

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